The present invention relates to a heat-developable photographic material. More specifically, the present invention relates to a heat-developable photographic material which causes almost no fog and has excellent storage stability.
A large number of photosensitive materials are known which have a photosensitive layer on a support and form an image by imaging exposure. An example of a system that enables environmental conservation or simplification of image formation includes a technique of forming an image by heat development.
In recent years, reduction of amount of waste processing solutions is strongly desired in the field of photomechanical processes from the standpoints of environmental protection and space savings. Techniques relating to photosensitive heat-developable materials for use in photomechanical processes are required which enables efficient exposure by a laser scanner or a laser image setter and formation of a clear black image having high resolution and sharpness. The photosensitive heat-developable materials can provide users with a simple and non-polluting heat development processing system that eliminates the use of solution-type processing chemicals.
Methods for forming an image by heat development are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075 and D. Morgan and B. Shely, Imaging Processes and Materials, xe2x80x9cThermally Processed Silver Systemsxe2x80x9d A, 8th ed., page 2, compiled by Sturge, V. Walworth and A. Shepp, Neblette (1969). The photosensitive material contains a reducible light-insensitive silver source (e.g., organic silver salt), a photocatalyst (e.g., silver halide) in a catalytically active amount, and a reducing agent for silver, which are usually dispersed in an organic binder matrix. This photosensitive material is stable at an ambient temperature, but when the material is heated at a high temperature (e.g., 80xc2x0 C. or higher) after light exposure, silver is produced through an oxidation-reduction reaction between the reducible silver source (which functions as an oxidizing agent) and the reducing agent. The oxidation-reduction reaction is accelerated by catalytic action of a latent image generated upon exposure. The silver produced by the reaction of the reducible silver salt in the exposure region provides a black image and this presents a contrast to the non-exposure region to form an image.
Fog is a serious problem for heat-developable photographic materials. Various researches have been made to reduce the fog in silver halide photosensitive materials for thermal photography. For example, U.S. Pat. No. 3,589,903 discloses use of mercury salts. Furthermore, there have also been disclosed uses of carboxylic acids such as benzoic acid and phthalic acid (U.S. Pat. No. 4,152,160), benzoyl benzoic acid compounds (U.S. Pat. No. 4,784,939), indane or tetralincarboxylic acids (U.S. Pat. No. 4,569,906), dicarboxylic acids (U.S. Pat. No. 4,820,617), heteroaromatic carboxylic acids (U.S. Pat. No. 4,626,500), halogenated compounds (U.S. Pat. Nos. 4,546,075, 4,756,999, 4,452,885, 3,874,946 and 3,955,982), halogen molecules or halogen atoms bound to a heterocyclic ring (U.S. Pat. No. 5,028,523), palladium compounds (U.S. Pat. No. 4,103,312 and British Patent No. 1,502,670), iron family metals (U.S. Pat. No. 4,128,428), substituted triazoles (U.S. Pat. Nos. 4,123,374, 4,129,557 and 4,125,430), sulfur compounds (U.S. Pat. Nos. 4,213,784, 4,245,033, and JP-A-51-26019 [the abbreviation xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d]), thiouracils (U.S. Pat. No. 4,002,479), sulfinic acid (JP-A-50-123331), metal salts of thiosulfonic acid (U.S. Pat. Nos. 4,125,403, 4,152,160 and 4,307,187), and combinations of metal salts of thiosulfonic acid and sulfinic acid (JP-A-53-20923 and JP-A-53-19825), thiosulfonic acid esters (JP-B-62-50810 [the abbreviation xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d], JP-A-7-209797 and JP-A-9-43760).
There has also been disclosed use of disulphide compounds (JP-A-51-42529 and JP-B-63-37368). However, those compounds have drawbacks, for example, insufficient anti-fog effect, decrease of Dmax (maximum image density) and sensitivity at a larger addition amount and the like.
Further, polyhalogenated compounds are extremely effective materials as an antifoggant for dry silver photosensitive materials, and such compounds have been disclosed in JP-B-54-165, European Patent Nos. 605981A, 631176A, U.S. Pat. Nos. 4,546,075, 4,756,999, 4,452,885, 3,874,946 and 3,955,982. However, those compounds have also drawbacks, for example, insufficient anti-fog effect, degraded storage stability, increase of the cost of photosensitive materials because of a large added amount.
Accordingly, an object of the present invention is to provide a heat-developable photographic material which can be manufactured at a low cost, and which causes much reduced fog and has good storage stability. The aforementioned object was achieved by the present invention.
The present invention thus provides:
(1) a heat-developable photographic material which comprises, on a support, (a) a reducible silver salt, (b) a reducing agent, (c) a binder, and (d) at least one polyhalogenated compound represented by the following formula (1):
Wxe2x80x94Lxe2x80x94Qxe2x80x94Y1xe2x80x94C(Z1)(Z2)xe2x80x94X1
wherein Z1 and Z2 represent a halogen atom, X1 represents a hydrogen atom or an electron withdrawing group, Y1 represents xe2x80x94COxe2x80x94 group or xe2x80x94SO2xe2x80x94 group, Q represents an arylene group or a divalent heterocyclic group, L represents a bridging group, and W represents carboxyl group or a salt thereof, slufo group or a salt thereof, phosphoric acid group or a salt thereof, a hydroxyl group, a quaternary ammonium group, or a polyethyleneoxy group.
According to preferred embodiments of the aforementioned invention, there are provided:
(2) the aforementioned heat-developable photographic material, which contains a photosensitive silver halide;
(3) the aforementioned heat-developable photographic material according to the aforementioned material (1) or (2), wherein Z1, Z2 and X1 represent a bromine atom, Y1 represents xe2x80x94SO2xe2x80x94 group, Q represents an arylene group or a divalent heterocyclic group, L represents an alkylene group, xe2x80x94Oxe2x80x94 group, xe2x80x94CONRxe2x80x94 group, xe2x80x94SO2NRxe2x80x94 group, or a group formed by a combination thereof wherein R represents a hydrogen atom or an alkyl group, provided that L contains at least one of xe2x80x94Oxe2x80x94 group, xe2x80x94NRCOxe2x80x94 group, and xe2x80x94SO2NRxe2x80x94 group, and W represents carboxyl group or a salt thereof, slufo group or a salt thereof, phosphoric acid group or a salt thereof, a hydroxyl group, a quaternary ammonium group, or a polyethyleneoxy group; and
(4) the aforementioned heat-developable photographic material which contains an ultrahigh contrast agent.
According to the present invention, there are provided heat-developable photographic materials with substantially no fog and excellent storage stability.